1. Field of the Invention
The present invention relates to a CT computed tomograph, namely, an apparatus of tomography using rays and particularly to a CT computed tomograph which measures, in an non-invasive manner, changes in an oxidation-reduction action of cytoplasmic cytochrome as well as changes in an oxygenated state of hemoglobin and a blood quantity in an organ or other part of a human body or an animal body.
2. Description of the Background Art
FIG. 11 is a diagram showing a construction of a conventional apparatus for measuring metabolism in an organ of a body. FIGS. 12 and 13 are diagrams showing light paths detected in the conventional measuring apparatus.
The apparatus shown in FIG. 11 is described in Japanese Patent Laying-Open No. 115232/1982. In this example of FIG. 11, a near infrared radiation source 1 emits near infrared rays of different wavelengths alternately. The near infrared rays pass through the head 3 of a human body through an optical fiber 2 so that a detection system 4 measures the intensity of the rays. An adjuster 5 adjusts the speed and the order of monochromatic flashes and demodulates the detected light signal. A feedback adjusting system 6 maintains the light signal detected by one wavelength to be constant by negative electricity feedback adjustment of the detection sensitivity and corrects a change in the transmittivity caused by the change in the blood quantity of the examined organ during the transmission time. An output adjusting circuit 7 outputs a feedback voltage blood quantity indicating signal simultaneously with received reference and measurement signals.
In the above mentioned apparatus shown in FIG. 11, a beam of 700 nm to 1300 nm is applied to the head 3 and changes in the oxygenated state of hemoglobin in the brain, the quantity of blood and the oxidation-reduction action of cytoplasmic cytochrome are detected by detection of the light transmitted through the head 3. This detection makes use of the characteristics that there is a small peak at about 760 nm of deoxygenated hemoglbin using an isosbestic point 805 nm of hemoglobin as a reference wavelength and that there is an oxygen-dependent absorbant of cytochrome aa3 in the wavelength range from 700 nm to 1300 nm.
In addition, Japanese Patent Laying-Open No. 72542/1985 proposes a tissue metabolism measuring apparatus which makes it possible to observe quantitatively in a two-dimentional distribution the state of binding of protein with oxygen molecules such as hemoglobin or myoglobin in a living body and to observe in a two-dimensional distributin the oxygen density of cytocondolia based on the oxidized and reduced state of cytochrome groups as a constituent of a respiratory chain.
However, if light of 700 nm to 1300 nm having a higher transmittivity through the living body than a visible radiation range is applied to the living body and the light transmitted therethrough is detected, the incident light has a short wavelength compared with the size of hemoglobin. Consequently, the incident light is diffused and absorbed immediately after the incidence and the detected light catches the component of the diffused light.
Those characteristics are described for example in "Optical Diffusion in Blood" by C. C. Johnson, IEEE TRANSACTION ON BIO-MEDICAL ENGINEERING, Vol. BEM-17 No. 2, 1970, pp. 129-133.
More specifically, as shown in FIG. 12, if a detector 9 is adapted to detect light applied to the living body, the light detected by the detector 9 includes not only the light transmitted through a light path 10a connecting the incident light and the detector 9 as a straight line but also the light diffused and transmitted to the other light paths 10b and 10c than the light path 10a. Thus, whenever the transmitted light is detected, the paths through which the detected light passes in the living body cannot be specified and in the case of the apparatus as shown in FIG. 11, it is possible to obtain only information of the whole of the internal of the living body t be measured or information of a light path (shown by the hatched area in FIG. 13) having a considerably larger width than the light path 10a connecting the incident light and the detector 9. In the case of diagnosing clinically an organic disease such as interruption in blood circulation or the degree of such disease, the position of such disease is in question and the information of such a wide range of the internal of the giving body is useless.